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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

SUBCOOLED FLOW BOILING OF FC-72 IN VERTICAL SMALL DIAMETER TUBES

Get access (open in a dialog) DOI: 10.1615/IHTC16.mpf.023064
pages 6755-6760

Résumé

Subcooled flow boiling heat transfer experiments were conducted with FC-72 flowing upward in vertical tubes with inner diameter of 1.8 mm and heated length of 26.2, 39.7 and 49.2 mm. Exponentially increasing heat inputs with periods of 81.31 ms to 16.04 s were exerted on the tubes. The flow velocity varied from 3 to 5 m/s and the inlet liquid temperature changed from 293 K to 333 K at a fixed outlet pressure of 300 kPa. The steady state and transient flow boiling heat transfer processes are described in detail. The effects of flow velocity, outlet subcooling, L/d ratios (heated length to tube diameter ratios) and exponential periods of heat generation rate on subcooled flow boiling and its Critical Heat Flux (CHF) were explored. An empirical correlation for steady state flow boiling CHF was developed. The transient CHF due to exponentially increasing heat input could be divided into two groups for long and short periods. The two group CHF data correspond to different heat transfer processes. It indicates that there exist two different CHF mechanisms for long and short periods.